Using x = [1 0;0 1;0 -1.00002; -1 0; 0 2.0001; 0 -2; -2 0]; I still get one less s.v. for qp than libsvm (ie same values I get without perturbing). This remains the case when only perturbing one s.v. The most notable change is that the second weight entry grows, although the first and b also change.

Also, thanks to fgpancorbo for the code for getting w & b from libsvm. Useful for the future.

@patrickjtierney,

In z space X6 and X7 map to the same point in z space, i.e, X6 (0, -2) and X7 (-2,0) map to (3,5). I wonder if this has any effect on the computation.